Apparatus for indicating horsepower



June 25, 1946. su 2,402,719

APPARATUS FOR INDICATING HORSEPOWER Filed June 26, 1942 HORSEPOWER /N/ENTOR DONALD K. ALL/&ON .ay HARR/s, K/ECH, Fo TERGHARR/J I' :23 Frag FOR THE F/RM A TTORNE KS.

PetentedJune 25, 1946 UNITED APPARATUS FOR INDICATIN G HORSEPOWER Donald K. Allison, Beverly Hills, Calif.

Application June 26, 1942, Serial No. 448.675

` 7 Claims. (c. 'za-136 My invention relates to an apparatus !or determining torque or power transmitted by a rotating shaft and giving an indication thereof.

It has long been a desideratum to be able to measure torque or horsepower being transmitted by a shaft. Torque-determinative systems have been developed requiring electrical connections to and from the shaft and requiring complex electrical equipment, but such systems are open to many difiiculties and have not found wide commercial usage. It is an object of the present invention to provide a novel method and apparatus for torque determination which is relatively simple and free of troublesomeelectrical connections to the shat.

The problem of indicating directly the horsepower transmitted by a shaft (i. e., torque times revolutions per minute) is even more complex and has never been solved satisfactorily. It would be most desirable to have a direct-reading horsepower meter on many shafts, particularly those subjected to variations in torque, which might increase to a dangerous magnitude. This is true, for example, in ine-shaft-drive types of airplanes where the power is transmitted from the engine to the propeller through a relatively long (and desirably minimum weight) shaft, and where the correlation between engine and propeller may be such, under certain conditions, as to impose destructive torques on the shaft.

It is an object of the present invention to provide a novel apparatus for determining, and preferably directly indicating, the power being transmitted by a shaft.

Another object oi' the invention lies in the use of one or more beams of light in solving such problems and in the modulation thereof in response to shaft speed and/or torque.

In the preierred embodiment of the invention, one or more light beams are modulated in response to changes in torque in the shalt, and are used to establish a corresponding series of undulations whichmay be used in torque determination, or which may be combined or reacted with, or electrically multiplied by, another electric `varlatlon responsive to speed f the shaft to obtain power determinations, nd the provision of such systems is an object of the present invention.

It is often desirable to torque-modulate two light beams differentially, and it is an object of the present invention to do this either in a torquedeterminative or power-determinative system.

Further objects of the invention lie in the novel apparatus for light modulation and in the novel electrical circuit arrangements employed, all irrespective of employment in torque-responsive or power-responsive systems. These circuit arrangements include novel electrical multlplying system giving a reading of the product o! two electric variations.

Further objects and advantages of the invention will be made evident to those skilled in the art from the following description of a preferred embodiment of the invention.

Referring to the drawing:

Figures 1 and 2 diagrammatically illustrate individually a wiring diagram and a preferred embodime'nt of the light-modulation means and, taken together, show very dlagrammatically the primary features of the principal embodiment of the complete invention;

Figure 3 is a vertical sectional View of the shaft and one Shutter, taken as indicated by the line 3-3 of Figure 2;

Figures 4 and 5 are diagrammatic views illustrating one embodiment of the light-modulation means;

Figura 6 is a diagrammatic view illustrating an alternative light-modulation means;

Figures 7 and 8 illustrate diagrammatically a further embodiment of a light-modulation means employing a single light beam; and

Figure 9 is a face view of a direct-reading meter which can be employed with the invention.

In general, the invention involves determination of torque or horsepower by employment of a light beam directed substantially longitudinally along, but spaced from, a portion of the shaft periphery. This light beam is modulated by suitable means. For example, it can be partially or completely interrupted at a frequency proportional to shaft speed and it can be modulated in intensity in response to the torque in the shaft. The resulting light beam can be translated into a visible indication representing the actual' torque in the shaft. In the preferred embodiment, the modulated light beam is translated into corresponding electric undulations which are, in efiect, "multiplied" by another electric variation which varies substantially proportionally to shaft speed to obtain a product which represents the actual power transmitted by the shaft.

Within the scope of this invention, any one of a large number of means can be used for forming, modulating, or controlling the light beam, and any one of a number of different variants can be employed for utilization of the modulated beam in giving a desired indication, for example, through translation into corresponding electric undulations and using these in themselves or compared with other undulations to secure a. representation of torque or horseploying two differentially modulated light beams,`

together` with an electrical system controlled thereby, to produce an indication of horsepower. Such a system is shown generally in Figures 1 to 3, inclusive, which will be described specifically without intent to limit the invention to this embodiment,

Referring particularly to Figure 2, the rotating shaft is indicated by the numeral and turns about an axis A--A, being used for transmitting power from one position to another. The torque transmitted by this shaft results in a proportional twist thereof and the invention, in eifect, measures the twist between two positions spaced along the shaft.

Fixed to the shaft at one of these positions is a shutter I2, best shown in Figur-es 2 and 3 as comprising light-impeding blades or teeth !3 separated by light-transmitting spaces [4. The number of teeth is not critical but these teeth should preferably be spaced equally around the periphery of the shutter l2. A collar member 15 surrounds the shaft o and is fixed thereto in an adjustable manner, as by employment of a set screw !8. This collar member serves as a convenient means for fixing the shutter |2 to the shaft |0 and small screws IT are shown in this Capacity.

The collar member l5 provides a generally concal refiecting surface [8 adapted to receive light rays from a source IS after passage through a lens 20 and an aperture plate 2l, and serves to reflect these light rays in a direction which is generally along, but spaced from, the periphery of the shaft l0. The refiecting surface |8 may be merely a highly polished steel surface, though it is preferred to coat the corresponding angular surface of the collar member I 5 with a coating of reflecting material, such, for example, as polished chromium or vapor-deposited aluminum, to provide a good front-surface reflector.

In the illustrated embodiment, the aperture plate 2| provides rectangular apertures 22 and 23 which are usually disposed in alignment in a radial plane extending outward from the axis A-A but which, in the diagrammatic showing of Figure 2, are shown turned slightly from this position for purpose of clarity. The function of this aperture plate is to produce two downwardly-directed beams of light 25 and 28, indicated in Figure 2 by their central rays and indicated in Figure 4 by white rectangles. These beams of light impinge against the reflecting surface l8 at peripherally spaced positions separated by a distance substantially corresponding to the distance between spaces Il of the shutter l2. The reflected beams 21 and 28 are indicated in Figure 2 by their central rays and, in Figure 4, by shaded portions correspondingly numbered. The maximum width of the refiected beams 21 and 28 in a horizontal plane will be determned by the width of the spaces ll of the shutter I 2, and the downwardly-extending beams 25 and 28 may be of substantially equal width or may be of somewhat greater width. In both instances, however, each of the beams may be slightly converging or slightly diverglng. If it is desired to collimate the rays in such a beam, this may be accomplished by a suitable condensing lens system adjacent the source !9 or by use of a lens 4 means 30 through which pass the reflected beams 21 and 28, and which lens system may also be used to focus the rays or form a reflected beam which is of the same width at the shutter !2 as at a second position along the shaft. Due to the fact that the two vertical beams 25 and '26 impinge against the reilecting, surface !8 at sli y.

spaced peripheral positions, the 'refiected beams 21 and 28 will usually diverse slightly from each other, as suggested in Figure 4.

Means is provided at such second position along the shaft !0 for differentially modulating these refiected light beams 21 and 28 in response to torque in the shaft. In the preferred embodiment, this means may include a second shutter 3| at this second position and providing light-impecling portion in the form of blades or teeth 32 (see Figure 4) and light-transmitting portions in the form of light-transmitting spaces 33. In the preferred embodiment, the shutter 3I is substantially identical in shape with the shutter !2, and its angular relationship with the shutter |2 is best shown in Figure 4, which illustrates this ahgular relationship under a condition of zero torque in the shaft l. Under such conditions, one of the blades 32 interrupts, blocks, or absorbs a portion of the reflected beam 21 and transmits a portion of this beam, the transmitted portion being hereinafter referred to as a modulated light beam and being indicated in Figure 4 by the numeral 35. Similarly, another of the blades 32 interrupts, blocks, or absorbs a portion of the reflected beam 28 and transmits a portion of this beam, the transmitted .portion representing another modulated light beam, indicated in Figure 4 by the numeral 38.

These modulated light beams are directed toward, and are reflected from, a reflecting surface 31 provided by a collar member 38 Secured to the shaft |0 and to the shutter 3l, as previously described with reference to the collar member l5.` The upwardly-refiected rays are indicated by the numerals 39 and 40, the central rays thereof being shown in Figure 2 and these beams being indicated by white rectangles correspondingly numbered in Figure 4. It will be understood that the beams 39 and 40 are reflected in a radial or conical plane extending outward from the axis A-A but, for purpose of clarity, are shown diagrammatically in Figura 2 as diverging toward respective photo-cells 4l and 42 of Figure 1.

Any torque-produced twist in the shaft |0 between the shutters I 2 and 3l will change the angular relationship of the shutter 3| with respect to the shutter !2. It will be apparent that a twist in one direction will increase the intensity of the transmitted or modulated beam 35, while correspondingly decreasing the intensity of the transmitted or modulated beam 38, thus producing a diflerential variation in intensity. This condition is exemplified in Figure 5, in which the amount of light inthe modulated beam 35 is reduced while the amount of light in the modulated beam 38 is increased. A twist in an opposite direction will produce an opposite difierential efl'ect and the intensity of the transmitted or modulated beam 35 will decrease, while the intensity of the transmitted or modulated beam 38 will increase. The diflerential intensity will be proportional to the torque in the shatt l0 and all variations in intensity of the transmitted or modulated beams 35 and 36 will be transmitted to the photo-cells 4| and 42.

The .photo-calls 4| and 42, respectively receiving the modulated light of the beams 35 and 36, serve to translate these beams into corre sponding electric undulation which are preferably amplifled by being transmitted to grids 43 and 44 of a double triode 45 .providing a fllament means 46 and plates 41 and 40. The filament means 46 is energized from a battery A or from any other suitable source, and a battery C or other bias means serves to apply an appropriate bias potential to the grids 43 and 44 and to supply an Operating potential for the photo-cells 4| and 42.

' I 'he plate currents or potentials of the plates 41 and 48 represent amplified electric undulations corresponding to the undulations of the modulated light beams 39 and 40, respectively,

prising one embodiment of an electric multi-` plying device. The armature means 54 is pivoted to move about its vertical axis by pivot pins 56 and 51 in suitable Jewel bearings (not shown) the pivot pin 56 carrying a, pointer 58 moving adjacent a scale '59 (see Figura 9) calibrated directly in horsepower. The conductor 50 is connected to the pivot pin 56 through a spiral spring 60, and this pin is connected by a conductor 6! to one end terminal of the armature coil. Similarly. the conductor 49 is connected through a spiral spring 62 to the pivot ,pin 51,

and thence to the other end terminal of the armature coil. An insulating sleeve 63 surrounds the pivot pin 51 and is, in turn, surrounded by a conducting sleeve 64 connected by conductor 65 to the mld-tap of the armature coil. A spiral spring `'66 electrically connects this mld-tap to a conductor 61 extending to the common terminal 53 and to the positive terminal of a battery B. The B-potential supplied to the plate 41 traverses conductor 49, spring 62, .pivot pin 51, one-half of the armature coil, sleeve 64, spring 66, and conductor 61. The B-potential supplied to the plate 48 traverses conductor 50,

spring 60, pivot pin 56, one-half of the armature coil, sleeve 64, spring 66, and conductor 61.

Themagnetic flelds established by the two halves o! the armature coil are in opposition. Correspondingly, ii' the plate current controlled by the modulated light beam 39 exceeds the plate current controlled by the modulated light beam 40, the armature means 54 will produce a net magnetic field, with the flux in one direction while, ii' a reverse condition exists, the net magnetic field will produce a flux in the opposite direction.

If the armature means 54 is placed in a unidirectional constant-intensity magnetic field, sup plied, for example, by a field member 10, the syscbtained, I preier to establish a varlable-intensity magnetic field in which the armature is posltioned, this field varying in intensity with the speed of revolution of the shalt |0. In this way, the field produced by the field member 10 reacts with the net field produced by the armature means 54 in such way that the hand or pointer 58 moves through an angular 'distance which is proportional to the product o! torque and revolutions per minute, thus being capable oi' a direct indlcation of power transmitted through the shalt 10. One manner of` accomplishing such a vari ation in field strength substantially proportional to shatt speed and between the pole pieces of the field member 10 is shown diagrammatically in Figures 1 and 2 and will now be described.

Reterring particularly to Flgure 2, an auxiliary light source 12 produces light which is tormed into a beam, as by a lens 13 and the aperture of an aperture plate 14, this beam being directed vertically upward toward the reflecting surface !8, the center line oi' this beam being indicated by the numeral 15. This beam is reflected as a beam 1.6 and is controlled by passage through the shutter z. This beam is again reflected by a stationary refiecting means 11 mounted on a support 18 to produce a reflected beam 19 directed toward a photo-cell 80. As the shalt io turns, the successive teeth I 3 and spaces l4 of the shutter 12 serve to split up the constantly-reflected beam into a series of reflected beams which are re flected to the photo-cell 80 at a frequency which is directly proportional to the speed of the shai't |0. The photo-cell 80 translates these light impulses into corresponding electric undulations which are supplied through conductors 8l and 82 to the input of an amplifler 83, there being an energizing battery 84 in this input circuit. This amplifier is oi' a type capable of producing an output which is substantially proportional to the frequency ot input. such amplifiers are sometimes known in the art as inverter ampliflers. In Figure 1 is shown a circuit diagram for one embodiment of such an amplifler, described in detail in Henney, "Electron Tubes in Industry," (1934), page 209. This circuit will produce an output current substantially proportional to the input rrequency and which does not vary substantially with changes in input potential. The

tem thus far described can be made to indicate i torque, as will be' apparent !rom the description of the mode of operation hereinatter set forth. However, in the preferred embodiment illustrated, and` in which a direct reading or horsepower is latter feature is desirable in the invention inasmuch as it precludes undesirable variations due to minor changes in' light intensity of the source 12, as produced, for example, by .a change in the applied potential or a gradua decrease in intensity oi! the source with use.

The electric undulations from the photo-cell represent, in efl'ect, an interrupted direct our rent which is supplied to the input 'of the amplifier 83. With the double-tube type of amplifier disclosed, the output represents, substantially, a uni-directional'current which varies in intensity .With the frequency of the input undulations. This uni-directional output is transmitted through conductors 81 and 88 to an energizing winding 90 surrounding the field member 10. such a field member 10 establishes an electro-magnetlc field traversing the armature means 54, though it should be understood that an aircore system can be employed for establishing this field through energization or the winding 90 rather than the magnetic-member-core type of field shown in Figure 1.

The mode of operation of the embodiment shown in Flgures 1 and 2 is as follows. The

two downwardly-directed light beams 25 and 25 are constantly delivered to the reflecting surface interrupted so as to move toward the refiecting surface s only when the reflected beams 21 and 28 will "fill" the spaces or slots |4 in a manner suggested in Figures 4 and 5. On the other hand, it is Simpler to direct the beams and 26 continuously toward the reflecting surface, in which event these spaces or slots |4 are only partially "filled" in varying degree with the reflected beams preparatory to and after the "full" beam position suggested in Figures 4 and 5. Correspondingly, the width of the reflected beams 21 and 28 in a horizontal direction will vary and the quantum of light in the modulated beams 35 and 36 wil vary in an undulating manner even under a zero torque condition. However, the integrated quantum of light in the modulated beam 35 will be equal to the integrated quantum of light in 8 mature means 54, this field reacts with the electromagnetic field produced between the poles'of the field member 10 and causes the armature means 54 to turn to give an indication oi the actual power transmitted'by the shaft u. Any resulting tendency of the armature to vibrate under the pulsations of the net electric field can be damped by conventional means so that the pointer 58 of the meter does not substantially vibrate at a corresponding frequency. v

It' will be clear that the elements of the system are shown only diagrammatically in Figures 1 and 2. For example, no attempt has been made to show accurately the structural details o! the meter 55. In practice, conventional pole pieces are employed to bound the armature space and other reflnements are employed which, for purpose of Simplicity, are not herein-shown. The meter 55 may be a conventional dynamometertype meter, modified by addition of the spring 63, the sleeve 64, etc., to provide a center tap for the usually-continuous winding of the armature.

the modulated beam 36 under conditions of zero v torque, but these values will change difierentially in response to increased torque and this differential variation will be directional.

The undulating modulated beam 39 reflected to the, photo-cell 4| acts to establish corresponding undulations in the plate circut of the triode by the action of the grid 43, which controls electron flow from the filament means 45 to the plate 41.

A c'orresponding undulating current will thus appear in one half of the winding of the armature means 54. At the same time, the photo-cell 42 will translate the light undulations in the modulated refiected beam into corresponding electric undulations which are applied to the grid 44 to control the electron flow from the filament means 46 to the plate 48, and corresponding electric undulations will thus appear in the other half of the winding of the armature means 54. The two currents in the respective halves of this armature means tend to establish electromagnetic fields in opposite directions. Correspondingly, if the instantaneous or integrated plate currents are equal, there will be no net electromagnetic field developed by the armature means. However, an unbalance in one direction will establish a net electric field in one direction which is substantially proportional to the unbalance, and an unbalance in the other direction will establish a net electric field in the opposite direction which, again, is substantiall'y proportional to the unbalance.

It will be recognized that the currents delivered to the two halves of the armature means 54 are' pulsatin-g so that such net .electromagnetic fields produced by the armature means will also be of a pulsating character. such pulsations will occur at a frequency proportional to the speed of the' shaft o. It will also be apparent; however, that the armature means 54 is disposed in an electromagnetic field having a fiux density which is substantially proportional to shaft speed. If no net field is being produced by the armature means 54 due to current therethrough, there will be no deflection of this armature means and the meter 55 ,will indicate a condition of zero horsepower, representing zero torque in the shaft o. However, as soon as a net field is produced by the arof the shutter 3l.

Similarly, no attempt has been made to show accurately the exact shape of the various elements, particularly those of the lens system. It will be understood that the lenses 20 and 13 may be of the collimating type to produce parallel-ray beams or spherical lenses can be employed, particularly if the lens means 30 is used. This lens means may serve as a collimating means or it may be employed to control the size of the light beams at the shutter 3| to make these sizes substantially correspond to those adjacent the shutter !2 in the event that the shutters are of identical Construction. It will be apparent also that various changes can be made in the electrical circuit disclosed through employment of other means for amplifying and/or balancing the electric undulations against each other to produce a net undulation, and that the battery-energized triode circuits can be energized from other sources. Diagrammatically, Figure 1 also shows the light sources IS and 12 as being energized from the battery A through a switch 92, but other energizing sources can be employed without departing from the spirit of the invention.

In the embodiment of the invention shown in Figures -1 and 2, the light beams 25 and 26 are reflected to be transmitted through adjacent slots or spaces l4 of the shutter |2 but it will be clear that the beams can be more widely separated or, as suggested in Figura 6, the beams can be brought closer together so as to be under the control of, and pass through, the same space l4. In the latter instance, the light beams reflected from the reflecting surface 18 will be partially absorbed and partially transmitted by adjacent teeth |3 and, in addition, the transmitted portions oi the beams will be further moduiated by adjacent teeth 32 and the intervening space 33 In this connection, the shutter 31 will serve partially to absorb and' partially to transmit the beams and any torque in the shaft o will differentially change the transmitted portions.

Another modification which can be made in the embodiment suggested in Figures 2, 4, and 5 is to bring the adjacent boundaries of the two vertical beams 25 and 26 closer together, even to the extent of meeting, to form a single rectangular beam which reaches and is reflected from the refiecting surface l8. In the latter connection, the total width of the reflected beam in a horizontal plane may be such` as to cover completely two of the adjacent teeth l3 and the lntervening space.

It will be understood, also, that it is not always necessary to employ two differentially-modulated light beams and that a single beam can be utilized. For example, if one of the beams of Figure 2 is blocked and the other remains modulated in response to torque, corresponding electric undulations wil appear in one half of the winding of the armature mean 54 and reactive electromagnetic flelds will b established in the meter 55 to cause deection of the pointer 58. Modulation of the single light beam will change the intensity of the field produced by th armature mean 54 so that, by use of a differently calibrated scale on the meter 55, the system will still indicate power transmitted by the shaft o.

Figures 7 and 8 show another method of modulating a single beam in which th shutters [2 and a are relatively shifted in an angular position so that, as shown in Figure 7, a tooth |3 on the shutter |2 is longitudinally aligned with a space 33 of the shutter 3| under conditions of zero torque. Thus, the tooth !3 and the'tooth 32 operate alternately to block the reflected beam and prevent any passage of light to the receptive photo-cell when there is no torque in the shaft. Correspondingly, there will be no electric undulations delivered to the armature means of the meter 55 under such conditions of zero torque. However, as suggested in Figure 8, as soon as the shutter 3| is angularly shifted with respect to the shutter I 2 in response to appearance of torque in the shaft ll), this complete blocking action is modified to permit transmission of light to the photo-cell in proportion to the torque. For example, if the receptive tooth 32 of the shutter 3! is displaced in one direction, it will permit a fractional portion of the beam to be transmitted past an edge on thereof to reach the photo-cell. A torque in an opposite direction would displace this receptive tooth 32 in an opposite direction and would permit a fractiona portion of the beam to be transmitted past an opposite edge u to reach the photo-cell. If a non-directional torque indication is desired, both of such fractional transmitted portions can move to the same photocell. but if directional indications are desired, these fractional transmitted portions can move to separate photo-cells, e. g., those indicated by the numerals 41 and 42.

It will also be clear that the invention can be employed to determine or indicate torque in the shaft Io, rather than power transmitted thereby. For example, any of the previously-described torque-modulated systems can be used to energize the armature means 54 while disposed in an electromagnetic field which is either constant (as, for example, if the field member 10 is a permanent magnet) or pulsating at a frequency determined by the speed of rotation of the shaft o. In the latter instance, the output of the photo-cell 80 can be supplied to th winding 90 around the field member n without amplification, or a conventional amplifier can be used to establish a pulsating field which does not vary in intensity with speedbut the frequency of which is determined by shaft speed. It will be noted that the power-indicating system of Figures 1 and 2 acts, in eifect, to multiply electrically torque and speed to produce a reading of power, but either a, torqueresponsive or a speed-responsive system can be employed individually to give, respectively, indications of torque or speed of the shaft o. Also, in the complete system, it should be understood that various other speed-responsive means can be used with the torque-modulation means, and that various torque-modulated means employing one or more light beams can be employed with the speed-responsive means herein-disclosed without departing from the spirit of the invention.

While the complete system of Figures -1 and 2- discloses a separate light beam for the speedresponsive system, e. g., the light beam 15, the invention contemplates also the possibility of employin in this crnnection a light beam derived from the source !9, for example, one of the refiected beams 21 and 28. For example, the reflector 11 can be disposed in one of these beams, the other being modulated in response to torque by the shutter 3! or the reflector 11 may be thus disposed and present a semi-mirrored surface to reflect a portion of the beam and transmit another portion.

It should be apparent, also, that it is not essential to use shutters l2 and 3| which provide as many teeth and spaces as are shown. A lesser number of teeth or spaces will produce undulations of lower frequency delivered to the meter 55 and the number of such teeth can be modified, even to the extent of using only one or two teeth on each shutter, without departing from the spirit of the invention.

In speaking of modulation of the intensity of a light beam, I have reference either to a change in light density in a beam of substantially constant dimensions or, as in the preferred embodiment, a change in intensity as produced by a light beam of substantially constant light density but varying in size or quantum of light. While the preferred embodiment of the invention employs a shutter providing opaque and transparent portions, it is quite apparent that such' portions on one or both shutters may be semi-opaque and semi-transparent or may vary in density around the periphery of the shaft in an undulating manner.

Various other changes and modiflcations will be apparent to those skilled in the art from the description and diagrammatic showing hereingiven, and it is intended that the invention be construed broadly to cover such alternative structures as are comprehended in the spirit of the appended claims.

I claim as my invention:

1. In a torque-responsive system for determining the torque acting to produce a twist in a shaft, the combination of: a substantially conical refiecting surface mounted on and concentric with the axis of said shaft; means for directing a pair of light beams toward said refiecting surface with axes aligned in a plane perpendicular to the shaft axis to be refiected in a direction along said shaft, the reflected beams diverging slightly from each other; light-sensitive means in the path of each refiected light beam; and means in the light path between said refiecting surface and said light-sensitive means for diflferentially varying the amount of said light in the two refiected beams reaching said light-sensitive means in response to a change in torque transmitted by said shaft.

2. In a torque-responsive system for determining the torque acting to produce a twist in a shaft, the combination of: a substantially conical reflecting surface mounted on and concentric with the axis of said shaft; means for directng light toward said refiecting surface to be reflected with 'diverging side boundaries in a direction along said shalt, said means including a first shutter secured to said shaft .at one position and providing a, light-impeding portion and a. li'ght-transmitting portion successively traversing said refiected light as said shaft rotates to direct the light with diverging side boundaries intermittently along said shaft, said light-transmitting portion providing two edges spaced circumferentially from each other for determining said diverging side boundaries of the refiected light; a second shutter secured to said shaft at another position and disposed in the path of the reflected light passed by said first shutter, said second shutter providin light-impeding means having two edges spaced circumferentially from each other and each bounding a light-transmitting space of said second shutter, these edges being spaced from each other a distance less than the distance between the diverging side boundaries of the reflected light whereby the reflected light is formed into two difierentially-varying beams, the first beam ncreasing and the second beam decreasing upon increase in torque in said shaft and the first beam decreasing and the second beam increasing upon decrease in said torque; and means responsive to the relative amount of light in these differentially-varying beams.

3. In a torque-responsive system for determining the torque acting to produce a twist in a shaft, the combination of: a conical member carried by said shaft to rotate therewith and providing a substantially conical reflecting surface concentric with the axis of said shaft; means !or directing light toward said reflecting surface to be reflected in a direction along said shaft; a first shutter secured to said shaft at one position and providing circumferentially-spaced openings with intervening blades successively traversing said reflected light as said shaft rotates to form an intermittent beam directed along said shaft; a second shutter secured to said shaft at another position and providing circumferentiallyspaced openings with' intervening vanes and disposed in said intermittent beam to partially transmit and partially impede same and to change the ratio of transnitted to impeded light in response to a twist of said shaft between said positions: a second conical member carried by said shaft to rotate therewith and providing a second substantially conical refiecting surface concentric with the axis of said shaft at a position beyond said second shutter to receive and reflect said transmitted light from said second shutter; and light-responsive means in the path of this refiected light responsive to a. change in the amount of light transmitted by said second shutter.

4. In a torque-responsive system for determining the torque acting to produce a twist in a shaft, the combination of: means for directing two beams of light longitudinally along the periphery of said shaft and substantially equidistant from the axis thereof from one position to another position, said means including a reflecting surface adjacent the periphery of said shaft, means for directing light thereto, and an aperture means for defining the boundaries of said beams; means for diiferentially impeding and` transmitting said light beams at said second position in response to a change in twist of said shaft by increasing and decreasing respectively the transmitted portions of said beams upon increase in twist of said shaft and decreasing and increasing same respectively upon decrease in 12 twist of said shalt: a first photo-cell receiving the transmitted light of one of said beams; a second photo-cell receiving the transmitted light of the other of said beams; an indicatlng means; and circuit means connecting 'said indicating means and said first and second photo-cells.

5. In a torque-responsive system for determining the torque in a shaft, the combination of: first and second shutters mounted on said shai't at axially spaced positions therealong, each of said shutters providing a plurallty of lighttransmitting spaces disposed equidistant from the axis of rotation of said shaft and providing lightimpeding portions separating said light-transmitting spaces; means for directing light toward said first shutter in a manner to produce two light beams masked by boundaries of adjacent light-transmitting spaces of said first shutter and directed toward said second shutter to be partially transmitted and partially impeded by the light-transmitting spaces and light-impeding portions of said second shutter to produce two modulated beams of light; photo-cell means in the path of light transmitted by said second shutter; and means operatively connected to said photo-cell means and responsive to a change in the relative amount of light in said modulated beams.

6. In a torque-responsive system for determining the torque in a shalt, the combination 01': a shutter mounted on -said shaft and providing a plurality of circularly disposed light-impeding elements separated by light-transmitting spaces; a light source; means tor masking the light from said source to form two light beams directed toward said shutter and generally along the periphery of said shaft at a position substantially equidistant from the axis of said shalt, said light beams being so spaced with respect to said shutter that beams of light pass simultaneously through adjacent light-transmitting spaces ot said shutter; means axially spaced from said shutter for difl'erentially modulating said light beams in response to torque in said shalt; and means responsive to the diflerentially modulated light beams.

7. In combination in a device responsive to changes in torque in a shaft: a substantially conical reflecting surface concentric with the axis ot said shalt; means for directing light toward said reflecting surface and i'or forming two reflected beams disposed side by side along the periphery of said shalt and substantially equidistant from the axis of said shai't, said reflected beams diverging slightly from each other, said means including a first shutter secured to said shaft at one position and providing two circumferentially-spaced beam-bounding edges !or respectively determining those side boundaries oi' the beams which are farthest rrom each other; a second shutter secured to said shaft in the path of the light beams moving through said first shutter, said second shutter providing two beambounding edges spaced closer together than said side boundaries of said beams to impede a portion o! each beam and transxnit another portion of each beam whereby a twist in said shalt between said shutters increases the light in the transmitted portion of one beam and decreases the light in the transmitted portion of the other beam; and means responsive to the relative amounts of light in the transmitted portions of the two beams.

. DONALD K. ALLISON. 

